diff --git a/manifests/prometheus-rules.yaml b/manifests/prometheus-rules.yaml
index 522433d1..aababcb5 100644
--- a/manifests/prometheus-rules.yaml
+++ b/manifests/prometheus-rules.yaml
@@ -330,7 +330,7 @@ spec:
         summary: Filesystem is predicted to run out of space within the next 4 hours.
       expr: |
         (
-          node_filesystem_avail_bytes{job="node-exporter",fstype!=""} / node_filesystem_size_bytes{job="node-exporter",fstype!=""} * 100 < 20
+          node_filesystem_avail_bytes{job="node-exporter",fstype!=""} / node_filesystem_size_bytes{job="node-exporter",fstype!=""} * 100 < 15
         and
           predict_linear(node_filesystem_avail_bytes{job="node-exporter",fstype!=""}[6h], 4*60*60) < 0
         and